<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        body>div{
            width: 200px;
            border: 1px solid red;
            /*当元素的所有子元素全部浮动时，自动识别的高度为0
            后面的元素会顶上来导致显示异常，添加overflow:hidden解决此异常*/
            overflow: hidden;

        }

        #d1{
            width: 50px;
            height: 50px;
            background-color: red;
            float: left;
        }
        #d2{
            width: 50px;
            height: 50px;
            background-color: green;
        }

        #d3{
            width: 50px;
            height: 50px;
            background-color: blue;
            float: right;
        }

    </style>
</head>
<body>

<div>
    <div id="d1"></div>
    <div id="d2"></div>
    <div id="d3"></div>
</div>
</body>
</html>